1. You press "SEND+drop mic" button (note how close the buttons are: http://imgur.com/5gBZVOh )
2. It says message sent and archived: http://imgur.com/GpOhiLY
3. Go to other recipient email, it contains attachment of mic drop image. http://imgur.com/Bs0iISe
4. Reply and it doesn't show up in inbox because conversation was archived (only accessible from "All Mail")